Numerous classes of chemical compounds exhibit varying degrees of antimicrobial or biocidal activity. Antimicrobial compositions are particularly needed in the food and beverage industries to clean and sanitize processing facilities such as pipelines, tanks, mixers, etc. and continuously operating homogenization or pasteurization apparatus. Sanitizing compositions have been formulated in the past to combat microbial growth in such facilities. For example, Grosse-Bowing et al., U.S. Pat. Nos. 4,051,058 and 4,051,059, teach peracetic acid materials. These peroxy-containing compositions are known for use in the production of microbiocidal agents. One such composition disclosed by Grosse-Bowing et al. contains peracetic acid, acetic acid or mixtures of peracetic and acetic acid, hydrogen peroxide, anionic surface active compounds such as sulfonates and sulfates, and water. Wang, U.S. Pat. No. 4,404,040, teaches a short chain fatty acid sanitizing composition comprising an aliphatic short chain fatty acid, a hydrotrope solubilizer capable of solubilizing the fatty acid in both the concentrate and use solution, and a hydrotrope compatible acid so that the use solution has a pH in the range of 2.0 to 5.0.
Peracetic acid has been shown to be a good biocide, but only at fairly high concentrations (generally greater than 100 part per million (ppm)). Similarly, peroxyfatty acids have also been shown to be biocidal, but only at high concentrations (greater than 200 ppm), such as in the composition disclosed in European Patent Application No. 233,731. Antimicrobial compositions having low use concentrations (less than 100 ppm) which effectively kill microbes are particularly desirable. Low concentrations minimize use cost, surface corrosion, odor, carryover of biocide into foods and potential toxic effects to the user. Therefore, a continuing need exists to provide such an antimicrobial composition for use in food processing, food service and health care facilities.
Combining a peroxygen source with an acid precursor in forming bleaching compositions or sanitizing compositions has been disclosed in the prior art. The prior art compositions are often formed in an aqueous solution which can be unstable, short lived, corrosive, and difficult to contain due to a need to vent the container containing the aqueous solution. Such compositions require high purity because impurities can catalyze decomposition of the peracid material. Aqueous solutions also require shipping of water which increases costs.
U.S. Pat. No. 5,296,239 to Colery, et al. and U.S. Pat. No. 5,736,497 to Steiner describe aqueous liquid peracid sanitizer formulations. International Publication No. WO 94/11483 describes the use of acylated citrate esters and ethoxylated alcohols as stabilizers. Solid mixtures are also known that generate peracid upon dissolution in aqueous media. U.S. Pat. No. 5,505,740 to Kong, et al. describes in situ formation of peracid where the aqueous wash solution is initially raised to a relatively high pH level by introduction of an alkaline agent for enhancing production of the peracid in the aqueous solution, then lowering the pH of the aqueous solution for enhancing bleach performance.
Aqueous peroxygen solutions containing perborates and/or hydrogen peroxide in combination with acids (e.g., boric acid) are often stabilized by the addition of a stabilizing agent. Stabilizing agents described in the prior art include carbazole sulfonates, diphenylamine sulfanates, N-phenylamino naphthalene sulfonates, and diethylenetriamine pentamethylene phosphonic acid. See U.S Pat. No. 5,736,497 to Steiner. This patent additionally describes the stabilization of alkaline hydrogen peroxide solutions by the addition of an organic stannate. U.S. Pat. No. 5,296,239 to Colery et al. describes stabilizing a thickened peracetic composition by adding sequestering agents, free-radical scavengers, and mixtures of sequestering agents and free-radical scavengers.
Techniques for enhancing performance of preformed peracids have been disclosed by a number of prior art references. In particular, U.S. Pat. No. 4,391,725 to Bossu discloses a granular hydrophobic peroxyacid laundry product in the form of a preformed peracid bleach provided within a pouch. An acid additive, indicated as having a pKa of from about 2 to about 7, is combined with the hydrophobic peracid in the pouch in order to aid in release of the peracid from the pouch, thereby enhancing bleach performance. U.S. Pat. No. 4,391,723 to Bacon et al. and U.S. Pat. No. 4,391,724 to Bacon describe the inclusion of boric acid or other acids together with the preformed peracids for improving bleach performance.